This chapter discusses the specificity mapping of bacterial lectins by the inhibition of hemagglutination using deoxy and deoxyfluoro analogs of receptor–active saccharides. The lectin-saccharide interaction makes it possible to interfere with bacterial binding and provide an opportunity to develop antiadhesive agents for treating or preventing infections. Information on the molecular details of the interactions is obtained by the inhibition of lectin–saccharide binding using either whole bacteria or the purified lectins. The structural information obtained from receptor mapping with deoxy and deoxyfluoro analogs of saccharides is potentially useful for the design of antiadhesive drugs against bacterial infection. Such analogs have improved metabolic stability and uptake characteristics, which are important for their use as drugs. In addition, the saccharide analogs may be used as haptens on affinity chromatography gels for lectin purification. Attenuated binding between the protein and the saccharide hapten can be useful in cases where the protein binds its natural counterpart too strongly to permit efficient protein recovery. Such affinity chromatography gels are used for the preparation of the PapG/PapD complex, which is currently being crystallized for X-ray analysis.